Query about Voltage for etx-70 TELESCOPE

9v is the recommended voltage supplied by 6 AA 1.5v batteries, I used NIMH 2300ua rechargable but the voltage of these is 1.3v, so 6*1.3=7.8v
Im not sure if the telescope was operating correctly, how will the telescope behave with a small 12v motorcycle battery, will 12v cause damage? the current should not matter !
Charles

Im not sure if the telescope was operating correctly, how will the telescope behave with a small 12v motorcycle battery,

Depends. Are you trying to look through it, or drive it to work? :lol:

See if this helps;

www.qsl.net/dl1gsj/astronomy/astro/html/etx-reg.html
The ETX70 requires up to 500mA when running both motors at full speed and the autostar illumination being set to brightest possible. The telescope of mine is used in Alt/Az-mode with the autostar's illumination set to minimum (still rather bright) which results in a input current of about 200mA during tracking. My experience was, that the scope was running fine using accumulators, resulting in a voltage of 7.2V. I guessed that everything between 7V and 9V would be fine to run the scopes electronics.

It then goes on to explain how to build a regulator which allows you use a 12v battery.

Jhonan
Thanks for that link, i was outside last night but it was so bloody cold, things did not go right, im so bloody mean I wont buy Duracell throw away batteries, 45 euro spent on 12 aa 2350mah NIMH rechargable batteries wont go to waste, to anyone buying batteries do not dream of buying NICAD batteries as they are "very old hat" and have poor capacity.
O leary Camera world were charging €10 yesterday for 4 2000mah batteries while Sound Store (next door) were charging €14.95 for the same pack
Charles

The problem with NiCad batteries is tha they loose their electrical properties the colder they get. This also happens with regular batteries, but their minimum temperature before falling off in charge IS slightly lower than NiCad.

The paste in batteries which drives the electirc motive force is best when it is soft - don't know why. So, as it gets colder, they don't necessarily freeze, but their cohesiveness does become more solid, thus effecting the movement and/or dissipating the electrons.

I stand corrected, but this is the jist of why NiCads are useless in any outdoor equipment in winter.

Seanie.

Charles,
Going under the 9 volts probaily wont cause damage, its just that the scope might be abit slower when it slews across the sky.

Going over voltage is a seriously bad idea, its like driving you motorcycle too fast, something is going to give.

I used to run a car battery and a mototcycle battery in series to get the 18 volts needed to run my scope, once the batteries started to die, the drives would slow down and eventually the scope would stall.

(A note to classic LX200 owners, if the voltage of the supply drops too low, the scopes tries to compensate by drawing more current to keep the power up, dont go too far or you could blow the scopes fuse, you'll see the current LED get very big)

Charles,

Dave L is quite right. Using 12v may not do damage in the short term but might over time. If you have absolutely no other choice you might wanna build a little circuit with a voltage regulator to get the 9v required.

Clear skies,

David.